Data replication for backup and recovery purposes is generally achieved by creating a shadow copy of a storage volume. Such replication may be done, for example, using Volume Shadow Copy Service (VSS) utility of the Windows™ operating system. A VSS command may be issued to take a volume snapshot periodically such as, for example, every fifteen minutes, to ensure that all application data and data in a cache memory in the file system are flushed to disk.
Between volume snapshots, data operations performed on the files and/or directories of a volume may be recorded (as events) in a memory for determining the total changes to the volume data at a later time. One concern with managing such recorded operations is preserving those operations during a system malfunction incident such as, for example, memory overflow. In other words, if the operation recordation is halted or if the recorded operations are lost due to a system malfunction, it may be difficult to accurately determine and replicate the data changes or updates that affected the volume.
One way to determine the data changes between two snapshots may be to compare the snapshots on a file-by-file or directory-by-directory basis, and send the differences to a backup system or server. However, this process may be very slow, thereby negatively impacting the performance of the replication system.
Thus, it is desirable to preserve recorded operations during a system malfunction in a replication process without slowing down, or otherwise negatively impacting the replication process.